drm/amdkfd: Ignore bogus signals from MEC efficiently

MEC firmware sometimes sends signal interrupts without a valid context ID
on end of pipe events that don't intend to signal any HSA signals.
This triggers the slow path in kfd_signal_event_interrupt that scans the
entire event page for signaled events. Detect these signals in the top
half interrupt handler to stop processing them as early as possible.

Because we now always treat event ID 0 as invalid, reserve that ID during
process initialization.

v2: Update firmware version checks to support more GPUs
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_events.c

@@ -238,12 +238,24 @@ static int create_other_event(struct kfd_process *p, struct kfd_event *ev, const
 	return 0;
 }
 
-void kfd_event_init_process(struct kfd_process *p)
+int kfd_event_init_process(struct kfd_process *p)
 {
+	int id;
+
 	mutex_init(&p->event_mutex);
 	idr_init(&p->event_idr);
 	p->signal_page = NULL;
-	p->signal_event_count = 0;
+	p->signal_event_count = 1;
+	/* Allocate event ID 0. It is used for a fast path to ignore bogus events
+	 * that are sent by the CP without a context ID
+	 */
+	id = idr_alloc(&p->event_idr, NULL, 0, 1, GFP_KERNEL);
+	if (id < 0) {
+		idr_destroy(&p->event_idr);
+		mutex_destroy(&p->event_mutex);
+		return id;
+	}
+	return 0;
 }
 
 static void destroy_event(struct kfd_process *p, struct kfd_event *ev)
@@ -271,8 +283,10 @@ static void destroy_events(struct kfd_process *p)
 	uint32_t id;
 
 	idr_for_each_entry(&p->event_idr, ev, id)
-		destroy_event(p, ev);
+		if (ev)
+			destroy_event(p, ev);
 	idr_destroy(&p->event_idr);
+	mutex_destroy(&p->event_mutex);
 }
 
 /*
@@ -749,7 +763,7 @@ void kfd_signal_event_interrupt(u32 pasid, uint32_t partial_id,
 			 * iterate over the signal slots and lookup
 			 * only signaled events from the IDR.
 			 */
-			for (id = 0; id < KFD_SIGNAL_EVENT_LIMIT; id++)
+			for (id = 1; id < KFD_SIGNAL_EVENT_LIMIT; id++)
 				if (READ_ONCE(slots[id]) != UNSIGNALED_EVENT_SLOT) {
 					ev = lookup_event_by_id(p, id);
 					set_event_from_interrupt(p, ev);

drivers/gpu/drm/amd/amdkfd/kfd_int_process_v9.c

@@ -141,6 +141,25 @@ static void event_interrupt_poison_consumption(struct kfd_dev *dev,
 	}
 }
 
+static bool context_id_expected(struct kfd_dev *dev)
+{
+	switch (KFD_GC_VERSION(dev)) {
+	case IP_VERSION(9, 0, 1):
+		return dev->mec_fw_version >= 0x817a;
+	case IP_VERSION(9, 1, 0):
+	case IP_VERSION(9, 2, 1):
+	case IP_VERSION(9, 2, 2):
+	case IP_VERSION(9, 3, 0):
+	case IP_VERSION(9, 4, 0):
+		return dev->mec_fw_version >= 0x17a;
+	default:
+		/* Other GFXv9 and later GPUs always sent valid context IDs
+		 * on legitimate events
+		 */
+		return KFD_GC_VERSION(dev) >= IP_VERSION(9, 4, 1);
+	}
+}
+
 static bool event_interrupt_isr_v9(struct kfd_dev *dev,
 					const uint32_t *ih_ring_entry,
 					uint32_t *patched_ihre,
@@ -206,6 +225,20 @@ static bool event_interrupt_isr_v9(struct kfd_dev *dev,
 	if (WARN_ONCE(pasid == 0, "Bug: No PASID in KFD interrupt"))
 		return false;
 
+	/* Workaround CP firmware sending bogus signals with 0 context_id.
+	 * Those can be safely ignored on hardware and firmware versions that
+	 * include a valid context_id on legitimate signals. This avoids the
+	 * slow path in kfd_signal_event_interrupt that scans all event slots
+	 * for signaled events.
+	 */
+	if (source_id == SOC15_INTSRC_CP_END_OF_PIPE) {
+		uint32_t context_id =
+			SOC15_CONTEXT_ID0_FROM_IH_ENTRY(ih_ring_entry);
+
+		if (context_id == 0 && context_id_expected(dev))
+			return false;
+	}
+
 	/* Interrupt types we care about: various signals and faults.
 	 * They will be forwarded to a work queue (see below).
 	 */

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -1294,7 +1294,7 @@ extern const struct kfd_event_interrupt_class event_interrupt_class_v9;
 
 extern const struct kfd_device_global_init_class device_global_init_class_cik;
 
-void kfd_event_init_process(struct kfd_process *p);
+int kfd_event_init_process(struct kfd_process *p);
 void kfd_event_free_process(struct kfd_process *p);
 int kfd_event_mmap(struct kfd_process *process, struct vm_area_struct *vma);
 int kfd_wait_on_events(struct kfd_process *p,

drivers/gpu/drm/amd/amdkfd/kfd_process.c

@@ -1370,12 +1370,16 @@ static struct kfd_process *create_process(const struct task_struct *thread)
 	INIT_DELAYED_WORK(&process->eviction_work, evict_process_worker);
 	INIT_DELAYED_WORK(&process->restore_work, restore_process_worker);
 	process->last_restore_timestamp = get_jiffies_64();
-	kfd_event_init_process(process);
+	err = kfd_event_init_process(process);
+	if (err)
+		goto err_event_init;
 	process->is_32bit_user_mode = in_compat_syscall();
 
 	process->pasid = kfd_pasid_alloc();
-	if (process->pasid == 0)
+	if (process->pasid == 0) {
+		err = -ENOSPC;
 		goto err_alloc_pasid;
+	}
 
 	err = pqm_init(&process->pqm, process);
 	if (err != 0)
@@ -1424,6 +1428,8 @@ static struct kfd_process *create_process(const struct task_struct *thread)
 err_process_pqm_init:
 	kfd_pasid_free(process->pasid);
 err_alloc_pasid:
+	kfd_event_free_process(process);
+err_event_init:
 	mutex_destroy(&process->mutex);
 	kfree(process);
 err_alloc_process: